The long-term goal of this research is to determine to what extent hearing-impaired subjects' performance on speech perception tasks is caused by sensory deficits versus deficits in phonological and/or lexical representations in long-term memory. The major theoretical question addressed by the proposed projects is: What kinds of adult long-term memory representations of spoken language result from a lifetime of poor- quality auditory stimulation? The possibility of long-term memory involvement in speech perception deficits is suggested by the classical observation in audiology that speech perception is often poorer in prelingually hearing-impaired adults than would be predicted by audiological or psychophysical measures. A guiding hypothesis in the proposed projects is that long-term memory representations of spoken language are significantly affected by the quality of the auditory stimulation that is available during development and over the life span. Four research projects are proposed, each addressing a different facet of long-term memory involvement in speech processing. In order to separate sensory and long-term memory effects on performance, the proposed projects compare prelingually hearing-impaired subjects to post- lingually impaired subjects and to normal-hearing subjects with simulated hearing losses. Project I adapts the memory scanning paradigm for use with auditory and audio-visual stimuli, in order to adduce the processing stages at which sensory and long-term memory information interact. Project II further adapts the memory scanning paradigm in order to examine the processes underlying the ability to achieve categorical linguistic percepts given variable sensory information. Project II introduces two methodologies in order to investigate long-term memory representations of phonological regularities. Project IV adapts experimental paradigms from the auditory word recognition literature in order to address auditory and audio-visual word recognition processes in hearing-impaired subjects. The interdisciplinary projects proposed here anticipate the continued development of sophisticated and effective cochlear implants and wearable tactile aids. One major question these developments raise concerns the dependence of speech perception not only on immediate sensory information, but also on long-term memory representations of spoken language acquired during the language-learning period and across the life span. Results of the proposed research as well as the methodologies explored may contribute to future understanding of the benefits of technical sensory aids for hearing-impaired individuals.